Filtered Smoking Article

ABSTRACT

A filter element suitable for use as a cigarette filter includes at least one section of fibrous tow comprising at least one plasticizer, the plasticizer including a citric acid ester, such as triethyl citrate, present in an amount of no more than about 15 weight percent based on the total weight of the filter material, and an adsorbent material, such as a granular carbonaceous material. One exemplary filter element has two or more sections of cellulose acetate tow comprising triethyl citrate in an amount of no more than about 12 weight percent based on the total weight of the filter material, and a granular carbonaceous material dispersed within at least one section of cellulose acetate tow. Cigarettes incorporating the filter element and methods of extending shelf-life of cigarettes including an adsorbent material are also provided.

FIELD OF THE INVENTION

The present invention relates to tobacco products, such as smoking articles (e.g., cigarettes), and in particular, to filtered cigarettes.

BACKGROUND OF THE INVENTION

Popular smoking articles, such as cigarettes, have a substantially cylindrical rod shaped structure and include a charge, roll or column of smokable material, such as shredded tobacco (e.g., in cut filler form), surrounded by a paper wrapper, thereby forming a so-called “smokable rod” or “tobacco rod.” Normally, a cigarette has a cylindrical filter element aligned in an end-to-end relationship with the tobacco rod. Typically, a filter element comprises plasticized cellulose acetate tow circumscribed by a paper material known as “plug wrap.” Triacetin is a known plasticizer for use as an additive in cellulose acetate tow. See, for example, U.S. Pat. Nos. 3,144,024 to Eichwald and 3,424,172 to Neurath. Certain filter elements can incorporate polyhydric alcohols. See, for example, UK Pat. Spec. 755,475. Typically, the filter element is attached to one end of the tobacco rod using a circumscribing wrapping material known as “tipping paper.” It also has become desirable to perforate the tipping material and plug wrap, in order to provide dilution of drawn mainstream smoke with ambient air. Descriptions of cigarettes and the various components thereof are set forth in Tobacco Production, Chemistry and Technology, Davis et al. (Eds.) (1999). A cigarette is employed by a smoker by lighting one end thereof and burning the tobacco rod. The smoker then receives mainstream smoke into his/her mouth by drawing on the opposite end (e.g., the filter end) of the cigarette.

Certain cigarettes incorporate filter elements incorporating activated carbon or charcoal materials. For example, an exemplary cigarette filter can possess multiple segments, and at least one of those segments can comprise particles of high carbon-content materials. Various types of filters incorporating charcoal particles or activated carbon types of materials are set forth in U.S. Pat. Nos. 2,881,770 to Touey; 3,101,723 to Seligman et al.; 3,236,244 to Irby et al.; 3,311,519 to Touey et al.; 3,313,306 to Berger; 3,347,247 to Lloyd; 3,349,780 to Sublett et al.; 3,370,595 to Davis et al.; 3,413,982 to Sublett et al.; 3,551,256 to Watson; 3,972,335 to Tigglebeck et al.; 5,909,736 to Stavridis; and 6,537,186 to Veluz; US Pat. Appl. Pub. No. 2003/00340085 to Spiers et al.; US Pat. Appl. Pub. No. 2003/0106562 to Chatterjee; US Pat. Appl. Pub. No. 2006/0025292 to Hicks et al.; and PCT WO2006/103404 to Cashmore et al., all of which are incorporated herein by reference.

It would be highly desirable to provide a cigarette possessing a filter element incorporating a carbonaceous material, such as particles of activated carbon, wherein the filter element (i) incorporates a filter material and other filter component materials, (ii) possesses the ability to efficiently remove effective amounts of various gas phase components of mainstream tobacco smoke passing through that filter element, and (iii) exhibits an acceptable level of storage stability as defined, in part, by maintaining consistent and desirable sensory characteristics upon use by a smoker after six months or more of storage.

SUMMARY OF THE INVENTION

The present invention relates to filter elements for a smoking article, and in particular, a rod shaped smoking article (e.g., a cigarette). The smoking article includes a lighting end (i.e., an upstream end) and a mouth end (i.e., a downstream end). A mouth end piece is located at the extreme mouth end of the smoking article, and the mouth end piece allows the smoking article to be placed in the mouth of the smoker to be drawn upon. The mouth end piece has the form of a filter element. The filter element incorporates an effective amount of a carbonaceous material or other adsorbent, such as a charcoal or activated carbon type of material. The amount of carbonaceous material within the filter element is sufficient to alter gas phase components (e.g., reduce the levels of certain gas phase components) in the mainstream smoke passing through the filter element. The filter element also includes at least one section of plasticized fibrous tow, wherein the plasticizer is an ester of citric acid. The use of an ester of citric acid as a plasticizer improves storage stability of the filter element (and smoking articles incorporating the filter element) by reducing or eliminating the use of plasticizers that can degrade to form volatile compounds that produce undesirable sensory characteristics.

In one aspect, the invention provides a filter element suitable for use as a cigarette filter, comprising at least one section of fibrous tow comprising at least one plasticizer, the plasticizer including a citric acid ester present in an amount of no more than about 15 weight percent based on the total weight of the filter material, and an adsorbent material. Preferred citric acid esters have ester groups comprising C1-C10 alkyl groups, such as triethyl citrate. The fibrous tow is preferably a cellulose acetate tow.

One preferred adsorbent is a granular carbonaceous material. For example, the adsorbent material can be a granular carbonaceous material having a particle size between about 10 Mesh and about 400 Mesh, and the carbonaceous material can be present in an amount of between about 20 mg and about 500 mg.

In one preferred embodiment, the filter element suitable comprises two or more sections of fibrous tow comprising at least one plasticizer, the plasticizer including a citric acid ester present in an amount of no more than about 15 weight percent based on the total weight of the filter material, and a granular carbonaceous material dispersed within at least one section of fibrous tow.

In another preferred embodiment, the filter element comprises two or more sections of cellulose acetate tow comprising triethyl citrate in an amount of no more than about 12 weight percent based on the total weight of the filter material, and a granular carbonaceous material dispersed within at least one section of cellulose acetate tow, wherein the granular carbonaceous material has a particle size between about 10 Mesh and about 400 Mesh, and wherein the carbonaceous material is present in an amount of between about 20 mg and about 500 mg.

In another aspect of the invention, a cigarette is provided, the cigarette comprising a tobacco rod having a smokable filler material contained within a circumscribing wrapping material, and the filter element according to the invention connected to one end of the tobacco rod. The filter element of the invention, as well as cigarettes made with the filter element, exhibit improved storage stability as compared to conventional adsorbent-containing filter elements comprising triacetin-plasticized fibrous tow. For example, filter elements of the invention can exhibit acceptable sensory characteristics after six months or more of storage. Thus, the invention also provides a method of improving storage stability of a plasticized, adsorbent-containing filter element, and smoking articles made therewith, by utilizing a citric acid ester as a plasticizer.

BRIEF DESCRIPTION OF THE DRAWING

In order to assist the understanding of embodiments of the invention, reference will now be made to the appended drawing, which is not necessarily drawn to scale. The drawing is exemplary only, and should not be construed as limiting the invention.

FIG. 1 is a cross-sectional view of a smoking article having the form of a cigarette, showing the smokable material, the wrapping material components, and the filter element of the cigarette.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

The present inventions now will be described more fully hereinafter with reference to the accompanying drawing. The invention may be embodied in many different forms and should not be construed as limited to the embodiments set forth herein; rather, these embodiments are provided so that this disclosure will satisfy applicable legal requirements. Like numbers refer to like elements throughout. As used in this specification and the claims, the singular forms “a,” “an,” and “the” include plural referents unless the context clearly dictates otherwise.

Referring to FIG. 1, there is shown a smoking article 10 in the form of a cigarette and possessing certain representative components of a smoking article of the present invention. The cigarette 10 includes a generally cylindrical rod 15 of a charge or roll of smokable filler material 16 contained in a circumscribing wrapping material 20. The rod 15 is conventionally referred to as a “tobacco rod.” The ends of the tobacco rod 15 are open to expose the smokable filler material. The cigarette 10 is shown as having one optional band 25 (e.g., a printed coating including a film-forming agent, such as starch, ethylcellulose, or sodium alginate) applied to the wrapping material 20, and that band circumscribes the cigarette rod in a direction transverse to the longitudinal axis of the cigarette. That is, the band 25 provides a cross-directional region relative to the longitudinal axis of the cigarette. The band 25 can be printed on the inner surface of the wrapping material (i.e., facing the smokable filler material), or less preferably, on the outer surface of the wrapping material. Although the cigarette can possess a wrapping material having one optional band, the cigarette also can possess wrapping material having further optional spaced bands numbering two, three, or more.

The wrapping material 20 of the tobacco rod 15 can have a wide range of compositions and properties. The selection of a particular wrapping material will be readily apparent to those skilled in the art of cigarette design and manufacture. Tobacco rods can have one layer of wrapping material; or tobacco rods can have more than one layer of circumscribing wrapping material, such as is the case for the so-called “double wrap” tobacco rods. Exemplary types of wrapping materials, wrapping material components and treated wrapping materials are described in U.S. Pat. No. 5,220,930 to Gentry; US Pat. Appl. Pub. No. 2004/0129281 to Hancock et al.; US Pat. Appl. Pub. No. 2005/0039764 to Barnes et al.; PCT WO2004/057986 to Hancock et al.; and PCT WO2004/047572 to Ashcraft et al., which are incorporated herein by reference.

At one end of the tobacco rod 15 is the lighting end 28, and at the other end is positioned a filter element 30. The filter element 30 positioned adjacent one end of the tobacco rod 15 such that the filter element and tobacco rod are axially aligned in an end-to-end relationship, preferably abutting one another. Filter element 30 may have a generally cylindrical shape, and the diameter thereof may be essentially equal to the diameter of the tobacco rod. The ends of the filter element 30 permit the passage of air and smoke therethrough.

The filter element 30 possesses a first filter segment 32 positioned adjacent one end of the tobacco rod 15. The first filter segment 32 includes a fibrous tow filter material 40 comprising a citric acid ester as a plasticizer that is over-wrapped along the longitudinally extending surface thereof with circumscribing plug wrap material 45. Within the filter material 40 of the first segment is dispersed a plurality of particles of carbonaceous material 50. Thus, in certain embodiments of the filter element of the invention including the embodiment shown in FIG. 1, at least a portion of the carbonaceous material 50, and typically virtually all of the carbonaceous material, is in intimate contact with a section of plasticized fibrous tow.

The filter element 30 possesses a second filter segment 55 longitudinally disposed relative to the first segment 32 and positioned at the extreme mouth end of the cigarette 10. The second filter segment 55 includes a fibrous tow filter material 60 comprising a citric acid ester as a plasticizer that is over-wrapped along the longitudinally extending surface thereof with circumscribing plug wrap material 65.

The filter element 30 is circumscribed along its outer circumference or longitudinal periphery by a layer of outer plug wrap 75. The outer plug wrap 75 overlies each of the first filter segment 32 and the second filter segment 55, so as to provide a combined, two segment filter element. The production of filter rods, filter segments and filter elements, and the manufacture of cigarettes from those filter rods, filter segments and filter elements can be carried out using the types of rod-forming units that have been employed to provide cigarette filters, multi-segment cigarette filters and filtered cigarettes. Multi-segment cigarette filter rods can be manufactured using a cigarette filter rod making device available under the brand name Mulfi from Hauni-Werke Korber & Co. KG of Hamburg, Germany. Other representative types of commercially available filter rod making equipment that can suitably modified for use include the KDF-2 unit available from Hauni-Werke Korber & Co. KG and the Decoufle unit available from Decoufle of France.

The filter element 30 is attached to the tobacco rod 15 using tipping material 88 (e.g., essentially air impermeable tipping paper), that circumscribes both the entire length of the filter element 30 and an adjacent region of the tobacco rod 15. The inner surface of the tipping material 88 is fixedly secured to the outer surface of the plug wrap 75 and the outer surface of the wrapping material 20 of the tobacco rod using a suitable adhesive; and hence, the filter element and the tobacco rod are connected to one another.

A ventilated or air diluted smoking article can be provided with an optional air dilution means, such as a series of perforations 92, each of which extend through the tipping material and plug wrap. The optional perforations 92 can be made by various techniques known to those of ordinary skill in the art, such as laser perforation techniques. Alternatively, so-called off-line air dilution techniques can be used (e.g., through the use of porous paper plug wrap and pre-perforated tipping paper).

The dimensions of a representative cigarette 10 can vary. Preferred cigarettes are rod shaped, and can have diameters of about 7.5 mm (e.g., circumferences of about 17 mm to about 27 mm, often about 22.5 mm to about 25 mm), and can have total lengths of about 70 mm to about 120 mm, often about 80 mm to about 100 mm. The length of the filter element 30 can vary. Typical filter elements can have lengths of about 15 mm to about 40 mm, often about 20 mm to about 35 mm.

Examples of fibrous tow for use in filter elements of the invention include cellulose acetate, polyolefin material such as polypropylene, or the like. One filter material that can provide a suitable filter rod is cellulose acetate tow having 3 denier per filament and 40,000 total denier. As another example, cellulose acetate tow having 3 denier per filament and 35,000 total denier can provide a suitable filter rod. As another example, cellulose acetate tow having 8 denier per filament and 40,000 total denier can provide a suitable filter rod. For further examples, see the types of filter materials set forth in U.S. Pat. Nos. 3,424,172 to Neurath; 4,811,745 to Cohen et al.; 4,925,602 to Hill et al.; 5,225,277 to Takegawa et al. and 5,271,419 to Arzonico et al.; each of which is incorporated herein by reference.

Triacetin is the conventional plasticizer used in cigarette filter element manufacturing. However, in certain filter designs, such as filter configurations comprising a carbonaceous material, it is possible for triacetin to degrade during extended periods of storage. Acetic acid, which is a possible degradation product of triacetin, is a highly volatile liquid at room temperature that exhibits a vinegary smell. The presence of an adsorbent material (particularly a carbonaceous adsorbent material) in intimate contact with a triacetin-plasticized fibrous tow can accelerate the rate of degradation of triacetin. Degradation of triacetin can impart undesirable sensory characteristics to the mainstream smoke produced during use of the cigarette. It would be advantageous to replace a plasticizer that can degrade to form a volatile degradation product associated with undesirable sensory characteristics with a plasticizer that, under normal usage and storage conditions, does not produce volatile degradation products that can adversely affect the sensory profile of mainstream smoke produced by the cigarette.

The present invention is based, in part, on the discovery that citric acid esters can be used advantageously as plasticizers in replacement of triacetin for adsorbent-containing filter elements. Under certain conditions, esters of citric acid can produce citric acid over time, which is a solid at room temperature and, thus, far less volatile and migratory than acetic acid. Citric acid does not have an objectionable odor, at least when present in a filter element under conditions of normal use. Thus, the combination of a citric acid ester plasticizer with an adsorbent material produces a filter element that exhibits enhanced storage stability as compared to a conventional triacetin-plasticized, adsorbent-containing filter element in terms of sensory characteristics.

The citric acid ester used in the present invention can vary. Each ester portion of the citric acid ester will typically include a C1-C10 alkyl group (i.e., carbon lengths of 1, 2, 3, 4, 5, 6, 7, 8, 9, or 10 carbon atoms), more preferably a C2-C5 alkyl group. “Alkyl” refers to a hydrocarbon chain, including cyclic hydrocarbon chains, which are preferably but not necessarily saturated, and which may be branched or straight chain. A particularly preferred citric acid ester is triethyl citrate, which is commercially available from Morflex, Inc. of Greensboro, N.C.

The amount of citric acid ester utilized in the present invention can vary. Typically, the filter element of the invention will include no more than about 15 weight percent of the citric acid ester, more preferably no more than about 12 weight percent, and most preferably no more than about 10 weight percent. The filter element will typically include at least about 3 weight percent, more preferably at least about 4 weight percent, and most preferably at least about 5 weight percent of the citric acid ester. In one embodiment, the citric acid ester is present in an amount of about 3 to about 15 weight percent (e.g., about 3, about 4, about 5, about 6 about 7, about 8, about 9, about 10, about 11, about 12, about 13, about 14, or about 15 weight percent), more preferably about 4 to about 12 weight percent, and most preferably about 5 to about 10 weight percent. The weight percentage of the citric acid ester is based on the total weight of the filter material.

All sections of plasticized filter material in the filter elements of the invention preferably comprise an amount of citric acid ester as a plasticizer, although in certain embodiments, some sections of plasticized filter material may not include the citric acid ester. For example, in one embodiment, the citric acid ester can be used as a plasticizer in only those filter segments in closest contact with the carbonaceous material, such as a filter segment having a carbonaceous material dispersed therein. In addition, each section of filter material in a filter element of the invention can contain different amounts of the citric acid ester plasticizer, and could contain a mixture of plasticizers, such as a mixture of a citric acid ester with triacetin or other conventional plasticizers. In embodiments where mixtures are utilized, the less preferred plasticizer (i.e., the plasticizer other than citric acid esters) will be utilized in amounts small enough to avoid the adverse sensory characteristics that can be associated with such plasticizers. Typically, the less preferred plasticizer would be used in amounts of less than about 2 weight percent.

During use, the smoker lights the lighting end 28 of the cigarette 10 using a match or cigarette lighter. As such, the smokable material 16 begins to burn. The mouth end of the cigarette 10 is placed in the lips of the smoker. Thermal decomposition products (e.g., components of tobacco smoke) generated by the burning smokable material 16 are drawn through the cigarette 10, through the filter element 30, and into the mouth of the smoker. During draw, certain amount of certain gaseous components of the mainstream smoke are removed from the mainstream smoke by the particles of carbonaceous material 50 within the filter element 30. Carbonaceous filter components, such as activated charcoal particles, have the capability of capturing a wide range of mainstream tobacco smoke vapor phase components. As noted above, the presence of certain commonly used components of filter elements (e.g., plasticizers such as triacetin) can produce volatile degradation products over time and under certain storage conditions, which could lead to a less desirable sensory experience upon use of the cigarette. However, the use of a citric acid ester as a plasticizer in the filter elements of the invention minimizes, and most preferably avoids, the adverse effects imparted by components such as triacetin, including adverse effects on the sensory characteristics of the cigarette.

Smokable materials and other associated materials useful for carrying out certain aspects of the present invention can vary. Smokable materials are materials that can be incorporated into the smokable segment or rod, and provide mass and bulk to some region within that smokable segment. Smokable materials undergo some type of destruction during conditions of normal use of the smoking article into which they are incorporated. Destruction of the smokable material, due at least in part to thermal decomposition of at least some component of that smokable material, results in the formation of an aerosol having the form normally characterized as “smoke.” For example, smokable materials incorporating tobacco materials are intended to burn, or otherwise undergo thermal decomposition, to yield tobacco smoke. The selection of tobacco types and tobacco blends can determine the chemical composition of, and the sensory and organoleptic characteristics of, that aerosol produced when that tobacco material or blend of tobacco materials is burned.

It is most highly preferred that smokable materials of the smokable segment incorporate tobacco of some form. Preferred smokable materials are composed predominantly of tobacco of some form, based on the dry weights of those materials. That is, the majority of the dry weight of those materials, and the majority of the weight of a mixture incorporating those materials (including a blend of materials, or materials having additives applied thereto or otherwise incorporated therein) can be provided by tobacco of some form. For example, those materials can be processed tobaccos that incorporate minor amounts non-tobacco filler materials (e.g., calcium carbonate particles, carbonaceous materials, grains or wood pulp) and/or binding agents (e.g., guar gum, sodium alginate or ammonium alginate); and/or a blend of those materials can incorporate tobacco substitutes or extenders. Those materials, and blends incorporating those materials, frequently are composed of greater than about 70 percent tobacco, often are greater than about 80 percent tobacco, and generally are greater than about 90 percent tobacco, on a dry weight basis, based on the combined weights of the tobacco, non-tobacco filler material, and non-tobacco substitute or extender. Those materials also can be composed of virtually all tobacco material, and not incorporate any non-tobacco fillers, substitutes, or extenders.

The smokable material can be treated with tobacco additives of the type that are traditionally used for the manufacture of cigarettes, such as casing and/or top dressing components. See, for example, U.S. Pat. Nos. 3,419,015 to Wochnowski; 4,054,145 to Berndt et al.; 4,887,619 to Burcham, Jr. et al.; 5,022,416 to Watson; 5,103,842 to Strang et al.; and 5,711,320 to Martin. Typical casing materials include water, sugars, and syrups (e.g., sucrose, glucose and high fructose corn syrup), humectants (e.g., glycerin or propylene glycol), and flavoring agents (e.g., cocoa and licorice). Those added components also include top dressing materials (e.g., flavoring materials such as menthol). See, for example, U.S. Pat. No. 4,449,541 to Mays et al. Additives also can be added to the smokable materials using the types of equipment described in U.S. Pat. No. 4,995,405 to Lettau, or that are available as Menthol Application System MAS from Kohl Maschinenbau GmbH. The selection of particular casing and top dressing components is dependent upon factors such as the sensory characteristics that are desired, and the selection and use of those components will be readily apparent to those skilled in the art of cigarette design and manufacture. See, Gutcho, Tobacco Flavoring Substances and Methods, Noyes Data Corp. (1972) and Leffingwell et al., Tobacco Flavoring for Smoking Products (1972).

Smokable materials typically are used in forms, and in manners, that are traditional for the manufacture of smoking articles, such as cigarettes. Those materials can incorporate shredded pieces of tobacco (e.g., as lamina and/or stem), and/or those materials can be tobacco materials that are in processed forms. For example, those materials normally are used in cut filler form (e.g., shreds or strands of tobacco filler cut into widths of about 1/10 inch to about 1/60 inch, preferably about 1/20 inch to about 1/35 inch, and in lengths of about ⅛ inch to about 3 inches, usually about ¼ inch to about 1 inch). Alternatively, though less preferred, those materials, such as processed tobacco materials, can be employed as longitudinally extending strands or as sheets formed into the desired configuration, or as compressed or extruded pieces formed into a desired shape.

Tobacco materials can include, or can be derived from, various types of tobaccos, such as flue-cured tobacco, burley tobacco, Oriental tobacco, Maryland tobacco, dark tobacco, dark-fired tobacco, and Rustica tobaccos, as well as other rare or specialty tobaccos, or blends thereof. Descriptions of various types of tobaccos, growing practices, harvesting practices and curing practices are set for in Tobacco Production, Chemistry and Technology, Davis et al. (Eds.) (1999). See also US Pat. Appl. Pub. No. 2004/0084056 to Lawson et al. Most preferably, the tobacco materials are those that have been appropriately cured and aged.

Typically, tobacco materials are used in a so-called “blended” form. For example, certain popular tobacco blends, commonly referred to as “American blends,” comprise mixtures of flue-cured tobacco, burley tobacco and Oriental tobacco. Such blends, in many cases, contain tobacco materials that have processed forms, such as processed tobacco stems (e.g., cut-rolled stems, cut-rolled-expanded stems or cut-puffed stems), volume expanded tobacco (e.g., puffed tobacco, such as dry ice expanded tobacco (DIET), preferably in cut filler form). Tobacco materials also can have the form of reconstituted tobaccos (e.g., reconstituted tobaccos manufactured using paper-making type or cast sheet type processes). Tobacco reconstitution processes traditionally convert portions of tobacco that normally might be wasted into commercially useful forms. For example, tobacco stems, recyclable pieces of tobacco and tobacco dust can be used to manufacture processed reconstituted tobaccos of fairly uniform consistency. The precise amount of each type of tobacco within a tobacco blend used for the manufacture of a particular cigarette brand can vary and is a manner of design choice, depending upon factors such as the sensory characteristics desired. See, for example, Tobacco Encyclopedia, Voges (Ed.) p. 44-45 (1984), Browne, The Design of Cigarettes, 3^(rd) Ed., p. 43 (1990) and Tobacco Production, Chemistry and Technology, Davis et al. (Eds.) p. 346 (1999). Various representative tobacco types, processed types of tobaccos, types of tobacco blends, cigarette components and ingredients, and tobacco rod configurations, also are set forth in U.S. Pat. Nos. 4,836,224 to Lawson et al.; 4,924,883 to Perfetti et al.; 4,924,888 to Perfetti et al.; 5,056,537 to Brown et al.; 5,159,942 to Brinkley et al.; 5,220,930 to Gentry; 5,360,023 to Blakley et al.; 5,715,844 to Young et al.; and 6,730,832 to Dominguez et al.; US Pat. Appl. Pub. Nos. 2002/0000235 to Shafer et al.; 2003/0075193 to Li et al.; 2003/0131859 to Li et al.; 2004/0084056 to Lawson et al.; 2004/0255965 to Perfetti et al.; 2005/0066984 to Crooks et al.; and 2005/0066986 to Nestor et al.; PCT WO02/37990 to Bereman; and Bombick et al., Fund. Appl. Toxicol., 39, p. 11-17 (1997), which are incorporated herein by reference.

The wrapping materials can vary. The tobacco rod can possess one layer of wrapping material or more than one layer of circumscribing wrapping material, such as is the case for the so-called “double wrap” tobacco rods. Exemplary types of wrapping materials, wrapping material components and treated wrapping materials are described in U.S. Pat. Nos. 5,105,838 to White et al.; 5,271,419 to Arzonico et al.; 5,220,930 to Gentry and 6,874,508 to Shafer et al.; PCT WO 01/08514 to Fournier et al.; PCT WO 03/043450 to Hajaligol et al.; US Pat. Appl. Pub. Nos. 2003/0114298 to Woodhead et al.; 2004/0134631 to Crooks et al.; 2005/0005947 to Hampl, Jr. et al.; 2005/0005947 to Hampl, Jr. et al.; 2005/0016556 to Ashcraft et al.; and 2005/0076929 to Fitzgerald et al.; and PCT WO2005/039326 to Rasouli et al.; which are incorporated herein by reference. Representative wrapping materials are commercially available as R. J. Reynolds Tobacco Company Grades 119, 170, 419, 453, 454, 456, 465, 466, 490, 525, 535, 557, 652, 664, 672, 676 and 680 from Schweitzer-Maudit International. Colored wrapping materials (e.g., brown colored papers) can be employed. Reconstituted tobacco materials also can be used, particularly as inner wrapping materials (e.g., in regions that are overwrapped with at least one further layer of wrapping material), and representative reconstituted tobacco materials useful as wrapping materials for smokable rods are set forth in U.S. Pat. No. 5,074,321 to Gentry et al.; 5,159,944 to Arzonico et al.; 5,261,425 to Raker; 5,462,073 to Bowen; and 5,699,812 to Bowen; which are incorporated herein by reference.

In certain preferred embodiments, the filter element of the invention incorporates a carbonaceous material. As used herein, “carbonaceous material” refers to a material that is composed primarily of carbon, and preferred carbonaceous materials are composed of virtually all carbon. Typically carbonaceous materials comprise carbon in amounts of more than about 85 percent, generally more than about 90 percent, often more than about 95 percent, and frequently more than about 98 percent, by weight. The carbonaceous material can have the form of charcoal, but most preferably is an activated carbon material. Activated carbon materials are high surface area materials. Exemplary activated carbon materials have surface areas of more than about 200 m²/g, often more than about 1000 m²/g, and frequently more than about 1500 m²/g, as determined using the Brunaver, Emmet and Teller (BET) method described in J. Amer. Chem. Soc., Vol. 60(2), pp. 309-319 (1938).

The carbonaceous materials can be derived from synthetic or natural sources. Materials such as rayon or nylon can be carbonized, followed by treatment with oxygen to provide activated carbonaceous materials. Materials such as wood and coconut shells can be carbonized, followed by treatment with oxygen to provide activated carbonaceous materials. The level of activity of the carbon may vary. Typically, the carbon has an activity of about 60 to about 150 Carbon Tetrachloride Activity (i.e., weight percent pickup of carbon tetrachloride). Preferred carbonaceous materials are provided by carbonizing or pyrolyzing bituminous coal, tobacco material, softwood pulp, hardwood pulp, coconut shells, almond shells, grape seeds, walnut shells, macadamia shells, kapok fibers, cotton fibers, cotton linters, and the like. Exemplary carbonaceous materials are coconut shell types of activated carbons available from sources such as Calgon Carbon Corporation, Gowrishankar Chemicals, Carbon Activated Corp. and General Carbon Corp. See, also, for example, Activated Carbon Compendium, Marsh (Ed.) (2001), which is incorporated herein by reference.

Examples of suitable carbonaceous materials are activated coconut hull based carbons available from Calgon Corp. as PCB and GRC-11 or from PICA as G277, coal-based carbons available from Calgon Corp. as S-Sorb, Sorbite, BPL, CRC-11F, FCA and SGL, wood-based carbons available from Westvaco as WV-B, SA-20 and BSA-20, carbonaceous materials available from Calgon Corp. as HMC, ASC/GR-1 and SC II, Witco Carbon No. 637, and AMBERSORB 572 or AMBERSORB 563 resins available from Rohm and Haas. Other carbonaceous materials are described in U.S. Pat. Nos. 4,771,795 to White et al. and 5,027,837 to Clearman et al.; and European Patent Application Nos. 419,733 and 419,981.

Certain carbonaceous materials can be impregnated with substances, such as transition metals (e.g., silver, gold, copper, platinum, and palladium), potassium bicarbonate, tobacco extracts, polyethyleneimine, manganese dioxide, eugenol, and 4-ketononanoic acid. The carbon composition may also include one or more fillers, such as semolina. Grape seed extracts may also be incorporated into the filter element 30 as a free radical scavenger.

Various types of charcoals and activated carbon materials suitable for incorporation into cigarette filters, various other filter element component materials, various types of cigarette filter element configurations and formats, and various manners and methods for incorporating carbonaceous materials into cigarette filter elements, are set forth in U.S. Pat. Nos. 3,217,715 to Berger et al.; 3,648,711 to Berger et al.; 3,957,563 to Sexstone; 4,174,720 to Hall; 4,201,234 to Neukomm; 4,223,597 to Lebert; 5,137,034 to Perfetti et al.; 5,360,023 to Blakley et al.; 5,568,819 to Gentry et al.; 5,622,190 to Arterbery et al.; 6,537,186 to Veluz; 6,584,979 to Xue et al.; 6,761,174 to Jupe et al.; 6,789,547 to Paine III; and 6,789,548 to Bereman; US Pat. Appl. Pub. Nos. 2002/0166563 to Jupe et al.; 2002/0020420 to Xue et al.; 2003/0200973 to Xue et al.; 2003/0154993 to Paine et al.; 2003/0168070 to Xue et al.; 2004/0194792 to Zhuang et al.; 2004/0226569 to Yang et al.; 2004/0237984 to Figlar et al.; 2005/0133051 to Luan et al.; 2005/0049128 to Buhl et al.; 2005/0066984 to Crooks et al.; 2006/0144410 to Luan et al; 2006/0180164 to Paine, III et al.; and 2007/0056600 to Coleman, III et al.; European Pat. Appl. 579410 to White; and PCT WO2006/064371 to Banerjea et al., which are incorporated herein by reference. Representative types of cigarettes possessing filter elements incorporating carbonaceous materials have been available as “Benson & Hedges Multifilter” by Philip Morris Inc., in the State of Florida during 2005 as a Philip Morris Inc. test market brand known as “Marlboro Ultra Smooth,” and as “Mild Seven” by Japan Tobacco Inc.

The filter element of the invention preferably incorporates an effective amount of a carbonaceous material, and particularly an effective amount of activated carbon. The effective amount is an amount that, when incorporated into the filter element, provides some desired degree of alteration of the mainstream smoke of a cigarette incorporating that filter element. For example, a cigarette filter element incorporating activated carbon particles or granules can act to lower the yield of certain gas phase components of the mainstream smoke passing through that filter element. Typically, the amount of carbonaceous material within the filter element is at least about 20 mg, often at least about 30 mg, and frequently at least about 40 mg, on a dry weight basis. Typically, the amount of carbonaceous material within the filter element does not exceed about 500 mg, generally does not exceed about 400 mg, often does not exceed about 300 mg, and frequently does not exceed about 200 mg, on a dry weight basis.

The carbonaceous material of the filter element is employed in a suitable form. For example, the carbonaceous material can have a form that can be characterized as powdered, granular, particulate, or the like. Typical particle sizes are greater than about 10 Mesh, often greater than about 20 Mesh, and frequently greater than about 30 Mesh. Typical particle sizes are less than about 400 Mesh, often less than about 300 Mesh, and frequently less than about 200 Mesh. The terms “granular” and “particulate” are intended to encompass both non-spherical shaped particles and spherical particles, such as so-called “beaded carbon” described in PCT WO03/059096 A1, which is incorporated by reference herein.

The moisture content of the carbonaceous material can vary. Typically, the moisture content of the carbonaceous material within the filter element, prior to use of the cigarette incorporating that filter element, is less than about 30 percent, often less than about 25 percent, and frequently less than about 20 percent, based on the combined weight of the carbonaceous material and moisture. Typically, the moisture content of the carbonaceous material within the filter element, prior to use of the cigarette incorporating that filter element, is greater than about 3 percent, often greater than about 5 percent, and frequently greater than about 8 percent, based on the combined weight of the carbonaceous material and moisture.

The carbonaceous material can be incorporated within a filter element by incorporating that carbonaceous material within paper or other sheet-like material (e.g., as a longitudinally disposed segment of gathered, shredded, or otherwise configured paper-like material), within a segment of a cavity filter (e.g., a particles or granules within the central cavity region of a three segment or stage filter element), or dispersed within a filter material (e.g., as particles or granules dispersed throughout a filter tow or gathered non-woven web material) as a segment of a longitudinally multi-segmented filter element. The carbonaceous material can be dispersed in the wrapping materials enwrapping the filter element or the carbonaceous material can be used in the form of carbon filaments inserted or woven into a section of filter material.

A typical cigarette filter element of the present invention possesses carbonaceous material within at least one component or segment of the filter element in a manner such that components of at least a portion of the filter element (e.g., filter additives such as a citric acid ester) comes into contact with the carbonaceous material within the filter element. Despite the intimate contact between certain filter additives, such as plasticizers, and the adsorbent material in certain embodiments of the filter element of the invention, the filter element does not exhibit the adverse storage characteristics associated with conventional adsorbent-containing filter elements plasticized with triacetin.

For the sake of brevity, carbonaceous materials are described throughout the specification as the adsorbent material of choice. However, the invention is not so limited, and the carbonaceous material could be replaced with any adsorbent material having a relatively high surface area capable of adsorbing smoke constituents without a high degree of specificity, or replaced with any adsorbent material that adsorbs certain compounds with a greater degree of specificity, such as an ion exchange resin. Exemplary alternative types of adsorbent 50 include molecular sieves (e.g., zeolites and carbon molecular sieves), clays, ion exchange resins, activated aluminas, silica gels, meerschaum, and mixtures thereof. Any adsorbent material, or mixture of materials, that has the ability to alter the character or nature of mainstream smoke passing through the filter element could be used without departing from the invention.

Other component segments of the filter element can vary. Representative filter element segments can incorporate the types of filter element components, designs and formats set forth in Browne, The Design of Cigarettes, 3^(rd) Ed. (1990); Tobacco Production, Chemistry and Technology, Davis et al. (Eds.) 1999; U.S. Pat. Nos. 4,508,525 to Berger; 4,807,809 to Pryor et al.; 4,903,714 to Barnes et al.; 4,920,990 to Lawrence et al.; 5,012,829 to Thesing et al.; 5,025,814 to Raker; 5,074,320 to Jones, Jr. et al.; 5,076,295 to Saintsing et al.; 5,101,839 to Jakob et al.; 5,105,834 to Saintsing et al.; 5,105,838 to White et al.; 5,271,419 to Arzonico et al.; 5,137,034 to Perfetti et al.; 5,396,909 to Gentry et al.; 5,595,218 to Koller et al.; 5,718,250 to Banerjee et al.; 6,530,377 to Lesser et al.; 6,615,842 to Cerami et al.; 6,631,722 to MacAdam et al.; and 6,792,953 to Lesser et al.; US Pat. Appl. Pub. Nos. 2002/0014453 to Lilly, Jr. et al.; 2004/0261807 to Dube et al.; 2005/0133052 to Fournier et al.; and 2006/0021624 to Gonterman et al.; which are incorporated herein by reference. Representative filter materials can be manufactured from tow materials (e.g., cellulose acetate or polypropylene tow) or gathered web materials (e.g., gathered webs of paper, reconstituted tobacco, cellulose acetate, polypropylene or polyester). While the filter element of the invention includes one or more sections of plasticized fibrous tow material, additional filter segments comprising other filtration materials can also be present without departing from the invention. The number of filter segments within the filter element of the invention can vary. In certain embodiments, the filter element can include 2-5 sections of plasticized filter material. For example, in a modification of the filter element shown in FIG. 1, a third section of plasticized filter material can be placed on the tobacco side of the filter segment containing the adsorbent material.

The plug wrap can vary. See, for example, U.S. Pat. No. 4,174,719 to Martin. Typically, the plug wrap is a porous or non-porous paper material. Plug wrap materials are commercially available. Exemplary porous plug wrap papers are available from Schweitzer-Maudit International as Porowrap Plug Wrap 17-M1, 33-M1, 45-M1, 65-M9,95-M9, 150-M4, 260-M4 and 260-M4T. Non-porous plug wraps exhibit porosities of less than about 10 CORESTA units, and preferably less than about 5 CORESTA units. Exemplary non-porous plug wrap papers are available as Ref. No. 646 Grade from Olsany Facility (OP Paprina) of the Czech Republic (Trierenberg Holding). Plug wrap paper can be coated, particularly on the surface that faces the filter material, with a layer of a film-forming material. Such a coating can be provided using a suitable polymeric film-forming agent (e.g., ethylcellulose, ethylcellulose mixed with calcium carbonate, or a so-called lip release coating composition of the type commonly employed for cigarette manufacture). Alternatively, a plastic film (e.g., a polypropylene film) can be used as a plug wrap material. For example, non-porous polypropylene materials that are available as ZNA-20 and ZNA-25 from Treofan Germany GmbH & Co. KG can be employed as plug wrap materials.

For cigarettes of the present invention that are air diluted or ventilated, the amount or degree of air dilution or ventilation can vary. Frequently, the amount of air dilution for an air diluted cigarette is greater than about 10 percent, generally greater than about 20 percent, often greater than about 30 percent, and sometimes greater than about 40 percent. Typically, the upper level for air dilution for an air diluted cigarette is less than about 80 percent, and often is less than about 70 percent. As used herein, the term “air dilution” is the ratio (expressed as a percentage) of the volume of air drawn through the air dilution means to the total volume and air and aerosol drawn through the cigarette and exiting the extreme mouth end portion of the cigarette. Higher air dilution levels can act to reduce the transfer efficiency of aerosol forming material into mainstream aerosol.

Preferred cigarettes of the present invention exhibit desirable resistance to draw. For example, an exemplary cigarette exhibits a pressure drop of between about 50 and about 200 mm water pressure drop at 17.5 cc/sec. air flow. Preferred cigarettes exhibit pressure drop values of between about 60 mm and about 180, more preferably between about 70 mm to about 150 mm, water pressure drop at 17.5 cc/sec. air flow. Typically, pressure drop values of cigarettes are measured using a Filtrona Cigarette Test Station (CTS Series) available form Filtrona Instruments and Automation Ltd.

Cigarettes of the present invention, when smoked, yield an acceptable number of puffs. Such cigarettes normally provide more than about 6 puffs, and generally more than about 8 puffs, per cigarette, when machine smoked under FTC smoking conditions. Such cigarettes normally provide less than about 15 puffs, and generally less than about 12 puffs, per cigarette, when smoked under FTC smoking conditions. FTC smoking conditions consist of 35 ml puffs of 2 second duration separated by 58 seconds of smolder.

Cigarettes of the present invention, when smoked, yield mainstream aerosol. The amount of mainstream aerosol that is yielded per cigarette can vary. When smoked under FTC smoking conditions, an exemplary cigarette yields an amount of FTC “tar” that normally is at least about 1 mg, often is at least about 3 mg, and frequently is at least about 5 mg. When smoked under FTC smoking conditions, an exemplary cigarette yields an amount of FTC “tar” that normally does not exceed about 20 mg, often does not exceed about 15 mg, and frequently does not exceed about 12 mg.

Filter elements of the present invention can be incorporated within the types of cigarettes set forth in U.S. Pat. Nos. 4,756,318 to Clearman et al.; 4,714,082 to Banerjee et al.; 4,771,795 to White et al.; 4,793,365 to Sensabaugh et al.; 4,989,619 to Clearman et al.; 4,917,128 to Clearman et al.; 4,961,438 to Korte; 4,966,171 to Serrano et al.; 4,969,476 to Bale et al.; 4,991,606 to Serrano et al.; 5,020,548 to Farrier et al.; 5,027,836 to Shannon et al.; 5,033,483 to Clearman et al.; 5,040,551 to Schlatter et al.; 5,050,621 to Creighton et al.; 5,052,413 to Baker et al.; 5,065,776 to Lawson; 5,076,296 to Nystrom et al.; 5,076,297 to Farrier et al.; 5,099,861 to Clearman et al.; 5,105,835 to Drewett et al.; 5,105,837 to Barnes et al.; 5,115,820 to Hauser et al.; 5,148,821 to Best et al.; 5,159,940 to Hayward et al.; 5,178,167 to Riggs et al.; 5,183,062 to Clearman et al.; 5,211,684 to Shannon et al.; 5,240,014 to Deevi et al.; 5,240,016 to Nichols et al.; 5,345,955 to Clearman et al.; 5,396,911 to Casey, III et al.; 5,551,451 to Riggs et al.; 5,595,577 to Bensalem et al.; 5,727,571 to Meiring et al.; 5,819,751 to Barnes et al.; 6,089,857 to Matsuura et al.; 6,095,152 to Beven et al; and 6,578,584 to Beven et al., which are incorporated herein by reference. For example, filter elements of the present invention can be incorporated within the types of cigarettes that have been commercially marketed under the brand names “Premier” and “Eclipse” by R. J. Reynolds Tobacco Company. See, for example, those types of cigarettes described in Chemical and Biological Studies on New Cigarette Prototypes that Heat Instead of Burn Tobacco, R. J. Reynolds Tobacco Company Monograph (1988) and Inhalation Toxicology, 12:5, p. 1-58 (2000); which are incorporated herein by reference.

Cigarette rods typically are manufactured using a cigarette making machine, such as a conventional automated cigarette rod making machine. Exemplary cigarette rod making machines are of the type commercially available from Molins PLC or Hauni-Werke Korber & Co. KG. For example, cigarette rod making machines of the type known as MkX (commercially available from Molins PLC) or PROTOS (commercially available from Hauni-Werke Korber & Co. KG) can be employed. A description of a PROTOS cigarette making machine is provided in U.S. Pat. No. 4,474,190 to Brand, at col. 5, line 48 through col. 8, line 3, which is incorporated herein by reference. Types of equipment suitable for the manufacture of cigarettes also are set forth in U.S. Pat. Nos. 4,781,203 to La Hue; 4,844,100 to Holznagel; 5,131,416 to Gentry; 5,156,169 to Holmes et al.; 5,191,906 to Myracle, Jr. et al.; 6,647,870 to Blau et al.; 6,848,449 to Kitao et al.; and 6,904,917 to Kitao et al.; and US Pat. Appl. Pub. Nos. 2003/0145866 to Hartman; 2004/0129281 to Hancock et al.; 2005/0039764 to Barnes et al.; and 2005/0076929 to Fitzgerald et al., each of which is incorporated herein by reference.

The components and operation of conventional automated cigarette making machines will be readily apparent to those skilled in the art of cigarette making machinery design and operation. For example, descriptions of the components and operation of several types of chimneys, tobacco filler supply equipment, suction conveyor systems and garniture systems are set forth in U.S. Pat. Nos. 3,288,147 to Molins et al.; 3,915,176 to Heitmann et al.; 4,291,713 to Frank; 4,574,816 to Rudszinat; 4,736,754 to Heitmann et al.; 4,878,506 to Pinck et al.; 5,060,665 to Heitmann; 5,012,823 to Keritsis et al.; and 6,360,751 to Fagg et al.; and US Pat. Appl. Pub. No. 2003/0136419 to Muller, each of which is incorporated herein by reference. The automated cigarette making machines of the type set forth herein provide a formed continuous cigarette rod or smokable rod that can be subdivided into formed smokable rods of desired lengths.

Filter element components or segments for filter elements for multi-segment filtered cigarettes typically are provided from filter rods that are produced using traditional types of rod-forming units, such as those available as KDF-2 and KDF-3E from Hauni-Werke Korber & Co. KG. Typically, filter material, such as filter tow, is provided using a tow processing unit. An exemplary tow processing unit has been commercially available as E-60 supplied by Arjay Equipment Corp., Winston-Salem, N.C. Other exemplary tow processing units have been commercially available as AF-2, AF-3, and AF-4 from Hauni-Werke Korber & Co. KG. In addition, representative manners and methods for operating a filter material supply units and filter-making units are set forth in U.S. Pat. Nos. 4,281,671 to Byrne; 4,862,905 to Green, Jr. et al.; 5,060,664 to Siems et al.; 5,387,285 to Rivers; and 7,074,170 to Lanier, Jr. et al. Other types of technologies for supplying filter materials to a filter rod-forming unit are set forth in U.S. Pat. Nos. 4,807,809 to Pryor et al. and 5,025,814 to Raker; which are incorporated herein by reference.

Multi-segment filter rods can be employed for the production of filtered cigarettes possessing multi-segment filter elements. An example of a two-segment filter element, as shown in FIG. 1, is a filter element possessing a first cylindrical segment incorporating activated charcoal particles dispersed within or throughout cellulose acetate tow (e.g., a “dalmation” type of filter segment) at one end, and a second cylindrical segment that is produced from a filter rod produced essentially of plasticized cellulose acetate tow filter material at the other end. Filter elements also can have the form of so-called “patch filters” and possess segments incorporating carbonaceous materials. Representative types of filter designs and components, including representative types of segmented cigarette filters, are set forth in U.S. Pat. Nos. 4,920,990 to Lawrence et al.; 5,012,829 to Thesing et al.; 5,025,814 to Raker; 5,074,320 to Jones et al.; 5,105,838 to White et al.; 5,271,419 to Arzonico et al.; 5,360,023 to Blakley et al.; 5,396,909 to Gentry et al.; and 5,718,250 to Banerjee et al; US Pat. Appl. Pub. Nos. 2002/0166563 to Jupe et al., 2004/0261807 to Dube et al.; 2005/0066981 to Crooks et al.; 2006/0090769 to Woodson; 2006/0124142 to Zhang et al.; 2006/0144412 to Mishra et al., 2006/0157070 to Belcastro et al.; and 2007/0056600 to Coleman, III et al.; PCT WO03/009711 to Kim; and PCT WO03/047836 to Xue et al., which are incorporated herein by reference.

Multi-segment filter elements typically are provided from so-called “six-up” filter rods, “four-up” filter rods and “two-up” filter rods that are of the general format and configuration conventionally used for the manufacture of filtered cigarettes can be handled using conventional-type or suitably modified cigarette rod handling devices, such as tipping devices available as Lab MAX, MAX, MAX S or MAX 80 from Hauni-Werke Korber & Co. KG. See, for example, the types of devices set forth in U.S. Pat. Nos. 3,308,600 to Erdmann et al.; 4,281,670 to Heitmann et al.; 4,280,187 to Reuland et al.; 4,850,301 to Greene, Jr. et al.; and 6,229,115 to Vos et al.; and US Pat. Appl. Pub. Nos. 2005/0103355 to Holmes, 2005/1094014 to Read, Jr., and 2006/0169295 to Draghetti, each of which is incorporated herein by reference.

The plasticizer component of the filter elements of the invention can be incorporated into a fibrous tow using methods and equipment known to one skilled in the art. For example, techniques and apparatus for plasticizer addition to fibrous tow are described in U.S. application Ser. No. 11/461,941 to Nelson et al., filed Aug. 2, 2006, and in U.S. Pat. Nos. 4,472,224 to Pryor; 4,525,385 to Pryor; 5,106,357 to Kampen; and 5,387,285 to Rivers, which are incorporated by reference.

The use of citric acid esters as a plasticizer in fibrous tow materials, such as cellulose acetate tow, can also be advantageous in applications other than cigarette filters. For example, fibrous tow materials used in industrial filtration media and ink pens could benefit from the use of citric acid esters as plasticizers.

Many modifications and other embodiments of the inventions set forth herein will come to mind to one skilled in the art to which these inventions pertain having the benefit of the teachings presented in the foregoing descriptions and the associated drawing. Therefore, it is to be understood that the inventions are not to be limited to the specific embodiments disclosed and that modifications and other embodiments are intended to be included within the scope of the appended claims. Although specific terms are employed herein, they are used in a generic and descriptive sense only and not for purposes of limitation. 

1. A filter element suitable for use as a cigarette filter, comprising at least one section of fibrous tow filter material comprising at least one plasticizer, the plasticizer comprising a citric acid ester present in an amount of no more than about 15 weight percent based on the total weight of the filter material, and an adsorbent material.
 2. The filter element of claim 1, wherein the adsorbent is a carbonaceous material.
 3. The filter element of claim 2, wherein the carbonaceous material is in granular form.
 4. The filter element of claim 1, wherein the citric acid ester comprises ester groups having C1-C10 alkyl groups.
 5. The filter element of claim 4, wherein the citric acid ester comprises ester groups having C2-C5 alkyl groups.
 6. The filter element of claim 5, wherein the citric acid ester is triethyl citrate.
 7. The filter element of claim 1, wherein the fibrous tow filter material is a cellulose acetate tow.
 8. The filter element of claim 1, comprising at least two sections of fibrous tow filter material comprising at least one plasticizer, wherein at least one section of fibrous tow filter material includes said adsorbent material dispersed therein.
 9. The filter element of claim 1, wherein the citric acid ester is present in an amount of about 5 to about 10 weight percent.
 10. The filter element of claim 1, wherein the adsorbent material is a granular carbonaceous material having a particle size between about 10 Mesh and about 400 Mesh, and wherein the carbonaceous material is present in an amount of between about 20 mg and about 500 mg.
 11. A filter element suitable for use as a cigarette filter, comprising two or more sections of fibrous tow filter material comprising at least one plasticizer, the plasticizer comprising a citric acid ester present in an amount of no more than about 15 weight percent based on the total weight of the filter material, and a granular carbonaceous material dispersed within at least one section of fibrous tow filter material.
 12. The filter element of claim 11, wherein the citric acid ester is present in an amount of about 5 to about 10 weight percent.
 13. The filter element of claim 11, wherein the granular carbonaceous material has a particle size between about 10 Mesh and about 400 Mesh, and wherein the carbonaceous material is present in an amount of between about 20 mg and about 500 mg.
 14. The filter element of claim 11, wherein the citric acid ester comprises ester groups having C1-C10 alkyl groups.
 15. The filter element of claim 14, wherein the citric acid ester comprises ester groups having C2-C5 alkyl groups.
 16. The filter element of claim 15, wherein the citric acid ester is triethyl citrate.
 17. A filter element suitable for use as a cigarette filter, comprising two or more sections of cellulose acetate tow comprising triethyl citrate in an amount of no more than about 12 weight percent based on the total weight of the filter material, and a granular carbonaceous material dispersed within at least one section of cellulose acetate tow, wherein the granular carbonaceous material has a particle size between about 10 Mesh and about 400 Mesh, and wherein the carbonaceous material is present in an amount of between about 20 mg and about 500 mg.
 18. A cigarette comprising a tobacco rod having a smokable filler material contained within a circumscribing wrapping material, and a filter element according to claim 1 connected to one end of the tobacco rod.
 19. A cigarette comprising a tobacco rod having a smokable filler material contained within a circumscribing wrapping material, and a filter element according to claim 11 connected to one end of the tobacco rod.
 20. A cigarette comprising a tobacco rod having a smokable filler material contained within a circumscribing wrapping material, and a filter element according to claim 17 connected to one end of the tobacco rod. 